Estimation of errors in the inverse modeling of accidental release of atmospheric pollutant: Application to the reconstruction of the cesium-137 and iodine-131 source terms from the Fukushima Daiichi power plant

A major difficulty when inverting the source term of an atmospheric tracer dispersion problem is the estimation of the prior errors: those of the atmospheric transport model, those ascribed to the representativity of the measurements, those that are instrumental, and those attached to the prior knowledge on the variables one seeks to retrieve. In the case of an accidental release of pollutant, the reconstructed source is sensitive to these assumptions. This sensitivity makes the quality of the retrieval dependent on the methods used to model and estimate the prior errors of the inverse modeling scheme. We propose to use an estimation method for the errors' amplitude based on the maximum likelihood principle. Under semi-Gaussian assumptions, it takes into account, without approximation, the positivity assumption on the source. We apply the method to the estimation of the Fukushima Daiichi source term using activity concentrations in the air. The results are compared to an L-curve estimation technique and to Desroziers's scheme. The total reconstructed activities significantly depend on the chosen method. Because of the poor observability of the Fukushima Daiichi emissions, these methods provide lower bounds for cesium-137 and iodine-131 reconstructed activities. These lower bound estimates, 1.2 × 10^16 Bq for cesium-137, with an estimated standard deviation range of 15%–20%, and 1.9 − 3.8 × 10^17 Bq for iodine-131, with an estimated standard deviation range of 5%–10%, are of the same order of magnitude as those provided by the Japanese Nuclear and Industrial Safety Agency and about 5 to 10 times less than the Chernobyl atmospheric releases.

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comments:

Anonymous
said...

it's a block roughly 50 by 50 by 50 meters.there's no smoke or fire.3 fat wires come out of it; these go to a city called tokyo with 10 million people. here they ride escalators and lifts and subways and take hot showers in the 20th floor and cook noodles with microwaves and read books at night and watch tv and... then the block blows up 300 meters high.we hear it's not bad, it's just a small block. sure, sure ...

"Institute of Radiation Protection and Nuclear Safety" is a french government owned agency that protects citizens from radiation (not a joke!). Their most efficient way to do that is the same than here in Japan, mainly stating that radiation is harmless at low dose. They don't mention the influence of smiling and stress yet, but it sure is a valuable addition that they will pick up sooner or later.

Another very fun fact is that this agency (called IRSN in french acronym) is the one that replaced the defunct SCPRI (Service Central de Protection contre les Rayonnements Ionisants) which means basically central agency for protection against radiation. They are the ones that said that Chernobyl nuke cloud was not going to enter France thanks to the Acores anticyclone pushing it away. They later realized contamination was increasing everywhere in France, and reassured the population because the level was supposedly harmless.

Boar game hunted in Europe still has high levels of contamination and it is advised to not eat it. In Germany, you can get a money compensation if the meat contamination is above the limit. Eating boar was banned in North-Eastern part of France, and IIRC the ban has been lifted last year.

Let's start with"Winiarek et al. (2012) estimated that the 137Cs and 131I releases by Fukushima were about a factor of 5–10 less than of Chernobyl."

SP: Old Vic has quite a cast of characters in Paris helping him assemble such half-assed guesses at the Centre d'Enseignement et de Recherche en Environnement Atmosphérique. I'm afraid I must discount pretty much of everything that gets filtered down from his ensemble and their partners at another French egghead bunch: The IRSN:

"The information available (video monitoring of the interior of the pools and measurements of water contamination) supports the hypothesis that there was no significant deterioration of the spent fuel stored. Reactor 4 has been unloaded and reactors 5 and 6 have been placed in a safe shutdown state."

"In particular, plutonium …was measured in the deposits formed in the northwest of the Fukushima Daiichi plant, but at very low levels, difficult to distinguish from the plutonium from fallout in the atmosphere produced by nuclear weapons testing."

Had to add this full paragraph from the IRSN medical deductions of the poor Japanese people:

"Out of the 3765 children examined by Fukushima Medical University, the thyroid examination showed normal results for 69.6%. At least one liquid cyst considered as subnormal (diameter less than 20 mm) was detected in 28.8% of the children. 1.5% of the children had at least one nodule, again considered as subnormal (diameter less than 5 mm).

At least one nodule of diameter greater than 5 mm was found in 0.7% of the children examined, but without any additional tests being necessary in the opinion of the physicians.Finally, no liquid cyst greater than 20 mm in diameter was detected."

SP: Yes…in America we call that abnormal, not puff it a bit by saying subnormal.

And for government doctors in Japan to say no additional tests are necessary…well I hope they sleep well at night covering up for their Tepco masters in Tokyo. I guess we all know who is really running that damaged country and it isn't the Diet.

At least these French 'navel' researchers openly admit that they are simply forming an educated guess based upon probably flawed & certainly incomplete data. Nice to know what the minimum contamination might be where the sun doesn't shine! We know what to ask of them next time they open their mouths to share such technicolor yawns!

Yes, this does sound like a pile of French crap (sorry). Higher estimates put amount of cesium at roughly equal to Chernobyl, and it is still leaking TRILLIONS of becs per day. Interesting ExSKF has not even visited the MEXT site to see that Tokyo drinking water has 0.007 bq/kg in the drinking water!

About my coverage of Japan Earthquake of March 11

I am Japanese, and I not only read Japanese news sources for information on earthquake and the Fukushima Nuke Plant but also watch press conferences via the Internet when I can and summarize my findings, adding my observations.

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